[infra] Use best practices for resource limits

[nicknovitski]

Why

This reflects some manual changes I made to reduce restarts of snackager.

How

• Set memory limits equal to memory requests
• Unset CPU limits

Ref: https://cloud.google.com/architecture/best-practices-for-running-cost-effective-kubernetes-applications-on-gke#set_appropriate_resource_requests_and_limits